The invention relates to improvements in polyester molding compositions.
Polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) have been widely used in molding compositions both with and without thermally stable reinforcing fibers such as glass fibers. Nucleated PET as described for instance in U.S. Pat. Nos. 4,357,268, 4,368,285 and 4,429,067 has also been frequently used in polyester molding compositions. Previously known polyester molding compositions of the type mentioned above, while satisfactory for many purposes, have been found unsatisfactory for use in applications such as electrical connecters where the heat and vapor from vapor phase soldering processes can affect the mechanical integrity of the plastic parts, resulting in undesirable conditions such as loosening of terminals, softening or melting of insulation, reflow of finishes at the contact areas and blistering and distortion of the part.
U.S. Pat. No. 4,251,429 discloses polyester molding compositions prepared from bisphenols and aromatic dicarboxylic acid such as isophthalic acid or terephthalic acid admixed with polyphenylene sulfide of the formula ##STR1## wherein n has a value of at least about 100. U.S. Pat. No. 4,140,671 discloses warp resistant, flame retarded, reinforced thermoplastic compositions comprising high molecular weight linear polyester resins such as polybutylene terephthalate and a warp resisting amount of polyphenylene sulfide powder, along with fiberglass, talc and flame retardants. Any of the commercially available polyphenylene sulfide powders are considered acceptable with the one known as Ryton V-1 sold by Phillips Petroleum Company being preferred. Ryton V-1 has a melt flow rate of about 4500.